Screening cognitive decline in older adults using umami hypogeusia and oral diadochokinesis: a cross-sectional study.

BACKGROUND: Early detection of cognitive decline is crucial for preventing progression to dementia. Although sensory impairments, such as olfactory and visual losses, have been identified as risk factors, the roles of gustatory and oral functions remain unclear. This study evaluated the association of taste perception and oral function, particularly oral diadochokinesis (ODK), with cognitive status in older dental outpatients. METHODS: A total of 58 outpatients aged ≥ 65 years were assessed using the Japanese version of the Montreal Cognitive Assessment (MoCA-J). Oral function was evaluated by measuring ODK, tongue pressure, occlusal force, and masticatory performance. Taste perception was assessed using the whole-mouth method across five basic tastes. Group comparisons were performed between cognitively normal and cognitively impaired participants. Receiver operating characteristic analysis and the Youden index were employed to identify optimal screening combinations. Multivariate logistic regression was used to assess the effects of age and sex. RESULTS: Cognitive decline (MoCA-J ≤ 25) was observed in 46.6% of the participants. The ODK performance for /ta/ and /ka/ as well as umami taste recognition, were significantly lower in the cognitively impaired group (P < 0.01). The combination of umami hypogeusia and reduced ODK /ka/ <5.7 repetitions/second had the highest diagnostic utility (Positive likelihood ratio, 2.30; specificity, 71.0%). Multivariate analysis confirmed that this combination was a significant predictor of cognitive decline (odds ratio, 4.727; P = 0.013). CONCLUSION: Umami hypogeusia and reduced ODK performance were significantly associated with cognitive impairment. This simple, noninvasive screening method may facilitate early detection of cognitive decline in routine dental care. TRIAL REGISTRATION: UMIN Clinical Trials Registry (UMIN-CTR), UMIN000057954. Registered retrospectively on 23 May 2025.